The herein disclosed invention finds applicability in the field of plastic foam manufacture and more particularly in the field of plastic blowing agents. More particularly, the invention herein disclosed is directed to producing blowing agents with reduced flammability.
Closed-cell polyurethane foams are widely used for insulation purposes in building construction and in the manufacture of energy efficient electrical appliances. In the construction industry, polyurethane (polyisocyanurate) board stock is used in roofing and siding for its insulation and load-carrying capabilities. Poured and sprayed polyurethane foams are also used in construction. Sprayed polyurethane foams are widely used for insulating large structures such as storage tanks, etc. Pour-in-place polyurethane foams are used, for example, in appliances such as refrigerators and freezers plus they are used in making refrigerated trucks and railcars. All of these polyurethane foams require expansion agents (blowing agents) for their manufacture. Insulating foams depend on the use of halocarbon blowing agents, not only to foam the polymer, but primarily for their low vapor thermal conductivity, a very important characteristic for insulation value. Historically, polyurethane foams are made with CFC-11(trichlorofluoromethane) as the primary blowing agent.
The art is continually seeking new fluorocarbon based azeotropic mixtures or azeotrope-like mixtures which offer alternatives for new and special applications for industrial cleaning, blowing agent and aerosol applications. Currently, fluorocarbon-based azeotrope-like mixtures are of particular interest because they are considered to be stratospherically safe substitutes for presently used fully halogenated chlorofluorocarbons (i.e., e.g., CFC-11, CFC-12, CFC-113). The latter have been implicated in causing environmental problems associated with the depletion of the earth""s protective ozone layer.
Accordingly, it is an object of the present invention to provide novel environmentally acceptable azeotrope-like compositions which are useful in a variety of applications including industrial cleaning, blowing agent and aerosol applications. More particularly, the herein disclosed invention is directed to formulations wherein the flammability of 2-chloropropane (IPC) is reduced so that it can be used in blowing agent applications.
The following U.S. patents are of interest as showing various blowing agent compositions, but do not disclose the inventive compositions disclosed herein.
Swan (U.S. Pat. No. 5,213,707) teaches an azeotrope-like mixture of 2-chloropropane and a chlorofluorohydrocarbon, as seen in col. 3, lines 40-55; however, this reference does not teach 2-chloropropane with a hydrofluorohydrocarbon per se. The composition of Swan always contains a chlorofluorohydrocarbon.
Ashida (U.S. Pat. No. 4,898,893) teaches isopropyl chloride as a blowing agent together with liquid chlorofluorocarbon as a blowing agent. This reference is deficient in not disclosing an azeotropic mixture with reduced flammability and specifically does not disclose fluorocarbons.
Monstrey (U.S. Pat. No. 5,064,872) discloses 2-chloropropane and chlorofluorohydrocarbons. This reference does not recognize the fact of no flash point or reduced combustibility of the herein disclosed invention. Nor is the recognition of azeotropic mixtures recognized.
A main object of the invention is to formulate non-flammable blowing agents.
A most significant object of this invention is to produce blowing agents containing 2-chloropropane which have reduced flammability.
A further object of this invention is the formulation of azeotropic mixtures which are useful in the formulation of blowing agents.
These and other objects of the present invention will become apparent from a reading of the following specification taken in conjunction with the enclosed drawings.
The herein disclosed invention is directed to formulations containing 2-chloropropane wherein the flammability of the 2-chloropropane has been reduced.
The herein disclosed invention relates to a polyisocyanurate foam or with polyurethane modified polyisocyanurate foam, which show very good fire-resistant and thermo-insulating properties.
The presently known polyisocyanurate foams and polyurethane modified polyisocyanurate foams, which are prepared by using a physical blowing agent, consisting of hydrochlorofluorocarbons, distinguish themselves as an insulation material by their good and lasting insulation coefficient, their good dimensional stability and their excellent fire behavior. It is accepted that the use of these hydrochlorofluorocarbon compounds as blowing agents, offer good fire-resistance and contribute to the excellent fire behavior of the foams concerned. As is well-known, such blowing agents show important drawbacks and nowadays it is accepted that they, in part, are responsible for the destruction of the ozone layer in the stratosphere and would, at the same time, increase the greenhouse effect on earth. Accordingly, the herein disclosed invention is intended to remedy these important drawbacks. A polyisocyanurate foam or polyurethane modified polyisocyanurate foam is proposed which shows the above mentioned beneficial properties, especially the good insulation coefficient and the excellent fire behavior, but not the disadvantages of the ones which are involved with the use of hydrochlorofluorocarbons, such as HCFC-141b. To this end, the polyisocyanurate foam or the polyurethane modified polyisocyanurate foam describes, according to the invention, closed cells wherein 2-chloropropane, in combination with hydrofluorocarbons and, if desired, pentanes are enclosed.
The invention relates also to a method for preparing the foam concerned, wherein a physical blowing agent is used for obtaining the foam structure, which method is characterized in that a 2-chloropropane containing physical blowing agent is applied. In a particular embodiment of the invention, use is made of a physical blowing agent consisting of at least 5% isopropyl chloride (2-chloropropane). 2-Chloropropane (isopropyl chloride) is a clear colorless liquid and has a flash point of xe2x88x9232xc2x0 C.
For the manufacture of these polyisocyanurate foams, use is essentially made of the mutual trimerization and other reactions of polyisocyanates, effected by typical catalysts. These polyisocyanurates are known for their exceptional fire behavior.
Since pure polyisocyanurate foams often have inadequate physical properties, they are in practice usually mixed with polyurethanes based on the same isocyanate and certain polyols, so that a reaction starts which develops synchronously with the trimerization. These foams are called polyurethane modified polyisocyanurates.
Besides the polyisocyanate, the polyols, the typical catalysts and the blowing agents, use is also made of foam stabilizers, flame extinguishing additives, etc.
The organic polyisocyanate compounds are of the R(NCO)n, wherein n greater than 2 and R represents an aliphatic or aromatic group. Preferably, use is made of diisocyanates or polyisocyanates comprising on average 2 to 4 isocyanate groups per molecule. A typical example thereof comprises diphenylmethane-4,4xe2x80x3-diisocyanate (MDI) and mixtures of the latter with its polymeric forms (xe2x80x9ccrudexe2x80x9dMDI), which are usually applied in the manufacture of rigid polyurethane foam and polyisocyanurate foam.
Under the influence of specific catalysts, such isocyanates can mutually react by dimerization and trimerization to form polyisocyanurate. In order to modify such polyisocyanurates with polyurethanes, each molecule with active hydrogen groups. E.g., Rxe2x80x94OH, R13 COOH, Rxe2x80x94SH, R2xe2x80x94NH, Rxe2x80x94NH2, Rxe2x80x94SH, . . . is in principle appropriate for use as reactive substrate. Preferable substrates include polyalcohols of the polyetherpolyol or polyesterpolyol type or mixtures thereof. A molecular weight  greater than 150, and preferably between 500 and 5000, is characterizing. The functionality is always higher or equal to 2 and an important property is a hydroxyl number (IOH) between 25 and 1000, more specifically between 150 and 850. Also, for this reaction, there exists more specific catalysts.
Where, for the preparation of polyurethane, use is made of an isocyanate index situated near the stoichiometric ratio, i.e., 95 to 110, a much higher index is necessary for the preparation of polyurethane modified polyisocyanurates so as to allow the mutual isocyanate trimerization reaction. Normally, this isocyanate index is  greater than 150.
In order to obtain the typical foam structure, it is necessary to make the foam using a chemical or physical blowing agent. As a chemical blowing agent, H2O is used, which liberates CO2 xe2x80x9cin situxe2x80x9d by reaction with isocyanate. As physical blowing agents, low boiling organic liquids are used which evaporate by the exothermic trimerization, urethane and urea reactions and lead also to the typical foam structure. As physical blowing agents, use is usually made of hydrochlorofluorocarbon compounds (HCFC""s), such as for example fluorodichloroethane also known as HCFC-141b. This blowing agent will be phased out of use beginning Jan. 1, 2003.
Broadly considered the herein disclosed invention is directed to compositions useful as blowing agents having no flash point or reduced combustibility comprising 2-chloropropane and an effective amount of a gas selected from the group consisting of a fluorohydrocarbon, perfluorocarbons, fluoroethers, hydrofluoropolyethers and mixtures thereof. Examples of the gas are perfluorocarbons selected from the group of octofluoropropane, hexafluoroethane, octafluorocyclobutane, perfluoropropylene, tetrafluoromethane and mixtures thereof; fluoroethers selected from the group consisting of bis(2,2,2-trifluoroethyl)ether, n-butyl-1,1,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,2-trifluoroethyl ether, ethyl 1,1,2,2-tetrafluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy) propane and mixtures thereof, and also a mixture of methyl nonafluoroisobutyl ether and methyl nonafluorobutyl ether; hydrofluoropolyethers selected from the group consisting of 1-difluoromethoxy-bis-(difluoromethyl ether, 1-difluoromethoxy-1,1,2,2-tetrafluoroethyl difluoromethyl ether and mixtures thereof; fluorohydrocarbon selected from the group consisting of 1,1,1,3,3 pentafluoropropane, 1,1,1,2,3,3,3 heptafluoropropane, 1,1,1,3,3,3 hexafluoropropane, 1,1,1,3,3 pentafluorobutane and 1,1,1,2 tetrafluoroethane; and the mixture of methyl nonafluoroisobutyl ether and methyl nonafluorobutyl ether and further mixtures thereof. Once the components producing blowing agents of no flash point or reduced combustibility are known, the optimum amounts to use can be determined by those skilled in the art.
Specific examples of compositions useful as a blowing agent having no flash point or reduced combustibility comprise about 80-90% of 2-chloropropane and about 10-20% of 1,1,1,3,3,3 hexafluoropropane; comprise greater than 0.5% to less than 50.2% of 2-chloropropane and 1,1,1,3,3 pentafluoropropane; comprise about 16.5 to 43.5% of 2-chloropropane and about 83.5 to 56.5% of 1,1,1,3,3 pentafluoropropane; comprise greater than 0.5% to less than 93% 2-chloropropane and the balance being 1,1,1,2,3,3,3 heptafluoropropane; comprise about 58 to 93% 2-chloropropane and about 42 to 7% 1,1,1,2,3,3,3 heptafluoropropane; an azeotrope-like mixture at one atmosphere of pressure comprising about 50-60% 2-chloropropane and about 40-50% 1,1,1,3,3 pentafluorobutane; an azeotrope-like mixture at one atmosphere of pressure comprising about 54% 2-chloropropane and about 46% 1,1,1,3,3 pentafluorobutane; and an azeotrope-like mixture at one atmosphere of pressure comprising about 78% 2-chloropropane and about 22% of a mixture of methyl nonafluoroisobutyl ether and methyl nonafluorobutyl ether.
Also contemplated by this invention are polyisocyanurate foams or polyurethane modified polyisocyanurate foams having a mainly closed cell structure, comprising closed cells wherein 2-chloropropane gas is enclosed in combination with a different gas or gases which lower the combustibility of the 2-chloropropane. The gas present in the cells comprises at least 5% by weight of 2-chloropropane.
The invention envisions a method for preparing mainly closed, cell shaped polyisocyanurate foam or polyurethane modified polyisocyanurate foam, wherein foam formation is performed with the use of a physical blowing agent comprising 2-chloropropane along with another gas which lowers the combustibility of the 2-chloropropane and wherein said physical blowing agent comprises at least 5% of 2-chloropropane. The 2-chloropropane can be used together with a hydrofluorocarbon blowing agent. The 2-chloropropane can be used in combination with other inert compounds having a relatively low boiling point or sublimation point. The amount of physical blowing agent used is comprised of between 1 and 50 parts by weight per 100 parts by weight of said polyisocyanurate foam or polyurethane modified polyisocyanurate foam. The hydrofluorocarbon blowing agent can be selected from the group consisting of tetrafluoroethane, pentafluoropropane, pentafluorobutane, heptafluoropropane, hexafluoropropane and pentafluoroethane. The inert compound can be selected from the group consisting of pentane, isopentane, cyclopentane, cyclopentene, methyl formate, dimethylether and diethylether. The physical blowing agent is used in an amount of between 1 and 30 parts by weight per 100 parts by weight of polyisocyanurate foam or polyurethane modified polyisocyanurate foam.
In this invention, the HCFC""s are replaced by 2-chloropropane mixtures. The mixtures are comprised of 2-chloropropane and blowing agents, such as for example, pentafluoropropane, pentafluorobutane, heptafluoropropane and hexafluoropropane (HFCs). Pentanes including normal pentane, isopentane and cyclopentane can be mixed with the 2-chloropropane and the HFCs and be used as blowing agents. The total blowing agent amount, which is used, is dependent on the foam density to be reached and on the molecular weight of the blowing agents. Amounts between 1 and 50% by weight, and preferably between 1 and 30% by weight, are typical. A most significant consideration is that the combustibility of 2-chloropropane is reduced or eliminated by the addition of selected additives. This allows normally combustible chloropropane to be used in blowing agent compositions.
As a foam stabilizer, silicon based products, such as polyalkylsiloxane polyether copolymers, are mostly used. Use can also be made of non silicon containing tensio-active substances. Preferably, amounts of 0.1-10 parts by weight, and more specifically between 0.5 and 2 parts by weight, are used per 100 parts by weight polyol.
Use is made, as a catalyst, of tertiary amine compounds, such as for example N,Nxe2x80x2-dimethylcyclohexylamine, diaminobicyclo-octane (DABCO), etc., or metal salts or alkali or alkaline-earth metal salts of organic or inorganic origin, such as for example potassium octoate and dibutyltin dilaurate.
Essentially, the balance between the trimerization reactions and the polyurethane formation is kept in equilibrium by means of these catalysts. The amounts which are used are dependent on the catalytic activity and are typically situated between 0.01 and 10 parts by weight, and more specifically between 0.01 and 4 parts by weight, per 100 parts by weight polyol.
Extra additives, such as for example fire retardants (phosphorus and halogen containing additives or polyols), smoke suppressors, additional cross-linkers, fillers, diluents, etc. can always be added to give the final product certain specific properties. This invention allows for the manufacture of foams either according to a continuous process, or to a discontinuous process, to prepare in the shape of plates (whether or not coated) blocks, in situ molded pieces and as sprayed foam.
It appears that the properties of these foams are comparable with those of HCFC blown foams. The foams with 1-chloropropane as blowing agent show however a slight tendency to shrink which may by useful for certain applications.
The invention is, of course, in no way limited to the here above described embodiments and several modifications can be taken into account within the scope of the invention, e.g., concerning the relative amounts of the as blowing agent used relative to the chloropropane and also concerning the composition of the reaction mixture for the polyisocyanurate foam or the with polyurethane modified polyisocyanurate foam preparation.
The nomenclature for the HFCs and HFEs are as follows:
HFC 245 fa 1,1,1,3,3 pentafluoropropane
HFC 227ea 1,1,1,2,3,3,3 heptafluoropropane
HFC 236 fa or FE 36 1,1,1,3,3,3 hexafluoropropane
HFC 365 mfc 1,1,1,3,3 pentafluorobutane
HFE 7100 3M Novec(trademark) mixture of methyl nonafluoroisobutyl ether and methyl nonafluorobutyl ether.
The use of blends of 2-chloropropane with perfluorocarbon compounds, hydrofluoroether compounds and hydrofluoropolyether compounds are also claimed as novel. A partial listing of the representative compounds is given below.
Perfluorocarbons
octofluoropropane
hexafluoroethane
octafluorocyclobutane
perfluoropropylene
tetrafluoromethane
Fluoroethers
bis(2,2,2trifluoroethyl) ether
n-butyl-1,1,2,2-tetrafluoroethyl ether
difluoromethyl 2,2,2-trifluoroethyl ether
ethyl 1,1,2,2-tetrafluoroethyl ether
1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy) propane
Hydrofluoropolyethers
1-difluoromethoxy-bis-(difluoromethyl ether
1-difluoromethoxy-1,1,2,2-tertrafluoroethyl difluoromethyl ether.
The purpose of the testing was to determine the amount of FE-36 required in a blend with isopropyl chloride (IPC) to suppress the IPC flash point under the DOT approved method ASTM D 3828 xe2x80x9cStandard Test Methods for Flash Point by SetaFlash Closed Testerxe2x80x9d. IPC has an extremely low flash point at xe2x88x9232xc2x0 C. (closed cup). The results suggest that a blend with between 80% and 90% IPC and 10% to 20% FE-36 may be non-flammable as defined by the method.
The following blends were tested with the SetaFlash Laboratory unit:
In the method, the flame must be pulled down into the cup and sweep across the sample surface quickly after the flame is applied for a true flash point. However, the xe2x80x9cflashbackxe2x80x9d observations for Sample #492-123-2 suggest that the 84% IPC level may be near the breakpoint for non-flammability. The xe2x80x9cflashbackxe2x80x9d occurred when the flame was applied and hovered over the liquid surface for a couple of seconds and then lifted from the open cup. Although this behavior is not uncommon for chlorinated solvents and not considered a true flash point, the fact that it occurred at the lowest measurable temperature suggests the blend may be near the flammability limits for IPC concentration.
The purpose of the testing was to determine the amount of HFC 245 fa required in a blend with isopropyl chloride (IPC) to suppress the IPC flash point under the DOT approved method ASTM D 3828 xe2x80x9cStandard Test Methods for Flash Point by SetaFlash Closed Testerxe2x80x9d. IPC has an extremely low flash point at xe2x88x9232xc2x0 C. (closed cup). Results were surprising in that a blend with as much as 43.5% IPC showed no flash point as defined by the method.
The following blends were tested with the SetaFlash laboratory unit:
The observations above were consistent with the typical character of chlorinated solvents in flash point testing. Usually, as the flash point temperature is approached, the applied flame becomes green and enlarged. However, this is not a flash point as defined by the ASTM method. In the method, the flame must be pulled down into the cup and sweep across the sample surface for a true flash point.
HFC 245 fa/cyclopentane blends were also tested for comparison to the previously studied HFC 245 fa/IPC blends flash-point results. No flash points were determined for either blend that had between 40% and 45% flammable component concentrations. However, the observations during the HFC 245 fa/IPC blend tests were similar to that seen with other chlorinated solvents in flash point testing. The HFC 245 fa/cyclopentane blend exhibited yellow flame burning throughout the temperature range of the test.
The purpose of the testing was to determine the amount of HFC 227 ea required in a blend with isopropyl chloride (IPC) to suppress the IPC flash point under the DOT approved method ASTM D 3828 xe2x80x9cStandard Test Methods for Flash Point by SetaFlash Closed Testerxe2x80x9d. IPC has an extremely low flash point at xe2x88x9232xc2x0 C. (closed cup). Results show that between 90% and 93% IPC concentrations have no flash point as defined by the ASTM method.
Results for flash point testing of HFC 227ea/IPC blends are shown in Table I. Flashback observations where shown are not true flash points as defined by the ASTM method.
The results suggest that an IPC concentration of between 89% and 93% blended with HFC 227ea may be considered non-flammable by the Standard DOT ASTM test.
This report summarizes the boiling point and azeotrope studies conducted on IPC/HFC blends. The purpose of the studies was to identify azeotropes or azeotropic-like compositions that could prove useful in foam blowing applications. HFC 245 fa and HFC 365 mfc were chosen for the studies because they are considered the most likely commercial high volume options in foam blowing applications.
Azeotropic mixtures or azeotrope-like mixtures exhibit either a maximum or a minimum boiling point. These mixtures have the same composition both in the liquid and the vapor and they can not be separated into their components by distillation. Therefore, boiling point curves were generated for both IPC/HFC 245 fa and IPC/HFC 365 mfc mixtures. The first boiling point measured was of one pure component and then measurements were taken upon gradual additions of the second component. The azeotropic mixture experiments were carried out at one atmospheric pressure.
1. Boiling point study results show no maximum or minimum boiling point for mixtures of IPC and HFC 245 fa.
2. A minimum boiling point of 33xc2x0 C.xc2x11xc2x0 C. at one atmosphere pressure was observed for a 39.95% HFC 365 mfc/60.05% IPC composition. A 32-plate Oldershaw distillation of a mixture of HFC 365 mfc and IPC showed an azeotropic composition of 54% IPC and 46% HFC 356 mfc at 33xc2x0 C.xc2x11xc2x0 C. at one atmosphere pressure.
3. No azeotropes were observed for mixtures of HFC 365 mfc, IPC and HFC 245 fa. In fact, the overhead temperatures at all times exceeded the boiling point of pure HFC 245 fa which is 15xc2x0 C. The overhead temperatures also remained lower than the boiling points for HFC 365 mfc and IPC which are 40xc2x0 C. and 36xc2x0 C., respectively.
1. Mini-ware glasswarexe2x80x94three necked 250 ml round bottom flask, 60 ml addition funnel with pressure equalization tube, condenser, thermowell
2. Digi-Sense Cole Palmer digital thermometer, J thermocouple
3. RM6 Lauda Brinkman circulator bath with ethylene glycol, Super RMT Lauda chiller
4. Research and Development pilot plant isopropyl chloride
5. HFC 245 fa, 1,1,1,3,3 pentafluoropropane, CAS 460-73-1, pressurized with nitrogen CAS 7727-37-9, Allied-Signal, Lot 1870
6. Teflon boiling chips
7. Variac heater
8. Solvay HFC 365 mfc Sample No. 492-157-1, Solkane(copyright) 1,1,1,3,3-pentafluorobutane
9. Oldershaw 32-plate distillation column
10. Chiller Neslab FTC350 coupled with Neslab EX211 bath with ethylene glycol/water.
11. Stainless steel cylinder 150 ml capacity
A gas chromatograph was used to determine HFC/IPC compositions. Sufficient cooling with ice, dry ice and chillers was required to adequately quantify the HFC 245 fa.
The apparatus was modified to allow better cooling of the condenser. A RM6 Lauda Brinkman circulator bath of ethylene glycol was used with a Super RMT Lauda chiller. The temperature was set to xe2x88x9215xc2x0 C. during the experiments. In addition, bubbler glassware was connected to the top of the condenser to verify sufficient cooling of the vapors. A Variac heater was used to add heat where necessary to boil the blends.
Boiling point measurements were taken using an ebulliometric technique.1 The flask was initially charged with HFC 245 fa and the boiling point was measured with the digital thermometer. Gradual additions of IPC were made and each was allowed to equilibrate at least 10 minutes before the boiling point temperature was recorded. The ambient barometric pressure was recorded during testing and the temperature readings were corrected as follows:
Corrected boiling point=F+0.06(760xe2x88x92P) where
F=observed boiling point
P=observed ambient barometric pressure, mm Hg 6 1 Annual Book of ASTM Standards, Vol. 15.05, ASTM D1120-93, xe2x80x9cStandard Test Method for Boiling Point of Engine Coolantsxe2x80x9d, p.7-9
A 32-plate Oldershaw distillation column was used to verify azeotropic mixtures. When HFC 245 fa was used in the composition, the Neslab chiller system was required to condense the overhead for sampling.